Added some comments in ascend.spec referring to as-yet-unresolved dependencies for documentation generation.
Added to doc/SConscript 'if' clause to turn off doc installation by default. Should allow 'scons install' to
occur without triggering documentation build.

Fixed the 'repeated test' bug (a static pointer to a destroyed symchar was being used in type.cpp)
Improved error reporting for 'not a refined solver_var' message.
Refactors Library::listModules and Library::getModules to use shared code.
TODO: find a more efficient solution to the static pointer problem above.

Adding the 'sun.c' and 'sun.h' files back into ASCEND so that we don't need dependency on libradtran.
Added detection of Scrollkeeper, the freedesktop.org documentation manager.
Added placeholder SConscript file for building the user's manual.